Do you think that humans will preserve different languages? If not, what will the only language look like?

We all know the importance of mastering different languages. A language is a cultural wealth, the indicator of centuries of a country’s evolution. Nowadays the language is still inherent in the identity of a country.

However, some languages have a special place among the others.
English is the international way of communication, spoken by approximately 360million people as a native language and more than one billion people as a foreign language.
The mandarin is spoken by more than 1,3 billion.

So the question is, do you think that one of those languages will take advantage of the others? If it is the case, will this language be the same as the actual language or it will be a mix of several languages, like the Esperanto for exemple?

I've heard that English nowadays is very different from that in the past. It's influenced by many people of different cultures. For example, it's said that "Long time no see" is from our Chinese. :) However, it's still English and people get used to all the changes quickly. So I personally think if a country or a place is open enough to the people all over the world, its language could merge with the new words and expressing ways. But their rooted culture should be preserved as a characteristic or a cultural legacy to be passed on. In that case, we can have more fun of varieties in the world. We can also learn different thought patterns or philosophies through different languages and their historic stories.

Dec 18 2013:
For a start, not all of China speaks Mandarin, and there is no significant demographic outside of china that speaks it either. You're nowhere near 1.3 billion.

Then you have to consider that most people who speak English are non-native speakers, meaning they utilize their first language for every day use, and only pull out their English on demand. Which means their native language preserves quite well.

We may in a few decades end up with a situation where almost everyone speaks English, but not as a first language, which means the other major languages will survive just fine.
While this new universal English will affect and be affected by other languages, it'll remain predominantly English.

Dec 20 2013:
Quentin, can I ask why you are asking the question, do you have a practical purpose in asking, or do you just find it interesting to think about? Does it seem like the best person to answer this would be someone who travels a lot, but I'm afraid I don't travel so it's very hard for me to answer.